inconsistent responses

Hell all,

I run VOCs (EPA method 524.2) on GC/MS (6890N/5973) using Teledyne Tekmar ATOMIX P&T. I have issues with some early eluters, mostly Vinyl Chloride, having very inconsistent IS response factors during calibrations. I am consistently having to drop my two lowest calibration levels in order to meet RSD criteria. For normal client work, this does not pose too big of an issue but it is causing issues with QC studies (LOQ, MDL, etc). Any thoughts would be greatly appreciated. Specs are as follows

Column: Agilent J&W DB-VRX 20mx0.18x1.0um

Split ratio: 50/1

Total flow: 28.4 mL/min

Initial temp: 30C for 3 min

Ramp 15 @ 190C then 20 @ 225 for 2 min

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paulsalverda 5 months ago

What maintenance has been done on the Atomix? How old is the trap? What flows and timings in the Tekmar, etc?

Historically this is related to moisture management or trap breakthrough.
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wjm011705 5 months ago in reply to paulsalverda

Both the transfer line and the moisture trap have been replaced in the last few months. The analytical trap is changed on a regular basis and was last done in December. The P & T method specifics are as follows. Thanks for the feedback!!

Purge: 11 min @ 40 mL/min

Dry purge time: 4 min @ 50 mL/min

Desorb time: 0.5 min @ 250C
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wjm011705 5 months ago in reply to paulsalverda

Both the transfer line and the moisture trap have been replaced in the last few months. The analytical trap is changed on a regular basis and was last done in December. The P & T method specifics are as follows. Thanks for the feedback!!

Purge: 11 min @ 40 mL/min

Dry purge time: 4 min @ 50 mL/min

Desorb time: 0.5 min @ 250C
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garyb007 5 months ago in reply to wjm011705

Dry purge at 50 I don't think is normal. I would try dry purge 2 min at 40.
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